diff mbox

[RFC,v1,08/10] spapr: CPU hotplug support

Message ID 1457074461-14285-9-git-send-email-bharata@linux.vnet.ibm.com (mailing list archive)
State New, archived
Headers show

Commit Message

Bharata B Rao March 4, 2016, 6:54 a.m. UTC 
Set up device tree entries for the hotplugged CPU core and use the
exising EPOW event infrastructure to send CPU hotplug notification to
the guest.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---
 hw/ppc/spapr.c                  | 73 ++++++++++++++++++++++++++++++++++++++++-
 hw/ppc/spapr_cpu_core.c         | 60 +++++++++++++++++++++++++++++++++
 hw/ppc/spapr_events.c           |  3 ++
 hw/ppc/spapr_rtas.c             | 24 ++++++++++++++
 include/hw/ppc/spapr.h          |  4 +++
 include/hw/ppc/spapr_cpu_core.h |  2 ++
 6 files changed, 165 insertions(+), 1 deletion(-)

Comments

David Gibson March 7, 2016, 3:49 a.m. UTC | #1 
On Fri, Mar 04, 2016 at 12:24:19PM +0530, Bharata B Rao wrote:
> Set up device tree entries for the hotplugged CPU core and use the
> exising EPOW event infrastructure to send CPU hotplug notification to
> the guest.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c                  | 73 ++++++++++++++++++++++++++++++++++++++++-
>  hw/ppc/spapr_cpu_core.c         | 60 +++++++++++++++++++++++++++++++++
>  hw/ppc/spapr_events.c           |  3 ++
>  hw/ppc/spapr_rtas.c             | 24 ++++++++++++++
>  include/hw/ppc/spapr.h          |  4 +++
>  include/hw/ppc/spapr_cpu_core.h |  2 ++
>  6 files changed, 165 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 5acb612..6c4ac50 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -603,6 +603,18 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
>      size_t page_sizes_prop_size;
>      uint32_t vcpus_per_socket = smp_threads * smp_cores;
>      uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
> +    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine());
> +    sPAPRDRConnector *drc;
> +    sPAPRDRConnectorClass *drck;
> +    int drc_index;
> +
> +    if (smc->dr_cpu_enabled) {
> +        drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, index);
> +        g_assert(drc);
> +        drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> +        drc_index = drck->get_index(drc);
> +        _FDT((fdt_setprop_cell(fdt, offset, "ibm,my-drc-index", drc_index)));
> +    }
>  
>      /* Note: we keep CI large pages off for now because a 64K capable guest
>       * provisioned with large pages might otherwise try to map a qemu
> @@ -987,6 +999,16 @@ static void spapr_finalize_fdt(sPAPRMachineState *spapr,
>          _FDT(spapr_drc_populate_dt(fdt, 0, NULL, SPAPR_DR_CONNECTOR_TYPE_LMB));
>      }
>  
> +    if (smc->dr_cpu_enabled) {
> +        int offset = fdt_path_offset(fdt, "/cpus");
> +        ret = spapr_drc_populate_dt(fdt, offset, NULL,
> +                                    SPAPR_DR_CONNECTOR_TYPE_CPU);
> +        if (ret < 0) {
> +            error_report("Couldn't set up CPU DR device tree properties");
> +            exit(1);
> +        }
> +    }
> +
>      _FDT((fdt_pack(fdt)));
>  
>      if (fdt_totalsize(fdt) > FDT_MAX_SIZE) {
> @@ -1181,7 +1203,7 @@ static void ppc_spapr_reset(void)
>  
>  }
>  
> -static void spapr_cpu_reset(void *opaque)
> +void spapr_cpu_reset(void *opaque)
>  {
>      sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
>      PowerPCCPU *cpu = opaque;
> @@ -1622,6 +1644,8 @@ static void spapr_boot_set(void *opaque, const char *boot_device,
>  void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
>  {
>      CPUPPCState *env = &cpu->env;
> +    CPUState *cs = CPU(cpu);
> +    int i;
>  
>      /* Set time-base frequency to 512 MHz */
>      cpu_ppc_tb_init(env, TIMEBASE_FREQ);
> @@ -1646,6 +1670,14 @@ void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
>          }
>      }
>  
> +    /* Set NUMA node for the added CPUs  */
> +    for (i = 0; i < nb_numa_nodes; i++) {
> +        if (test_bit(cs->cpu_index, numa_info[i].node_cpu)) {
> +            cs->numa_node = i;
> +            break;
> +        }
> +    }
> +

This hunk seems like it belongs in a different patch.

>      xics_cpu_setup(spapr->icp, cpu);
>      qemu_register_reset(spapr_cpu_reset, cpu);
>  }
> @@ -1768,6 +1800,7 @@ static void ppc_spapr_init(MachineState *machine)
>      char *filename;
>      int spapr_cores = smp_cpus / smp_threads;
>      int spapr_max_cores = max_cpus / smp_threads;
> +    int smt = kvmppc_smt_threads();
>  
>      if (smp_cpus % smp_threads) {
>          error_report("smp_cpus (%u) must be multiple of threads (%u)",
> @@ -1834,6 +1867,15 @@ static void ppc_spapr_init(MachineState *machine)
>          spapr_validate_node_memory(machine, &error_fatal);
>      }
>  
> +    if (smc->dr_cpu_enabled) {
> +        for (i = 0; i < spapr_max_cores; i++) {
> +            sPAPRDRConnector *drc =
> +                spapr_dr_connector_new(OBJECT(spapr),
> +                                       SPAPR_DR_CONNECTOR_TYPE_CPU, i * smt);
> +            qemu_register_reset(spapr_drc_reset, drc);
> +        }
> +    }
> +

Nit: would this be cleaner to include in the same loop that constructs
the (empty) links and boot-time cpu cores?

>      /* init CPUs */
>      if (machine->cpu_model == NULL) {
>          machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
> @@ -2267,6 +2309,27 @@ out:
>      error_propagate(errp, local_err);
>  }
>  
> +void *spapr_populate_hotplug_cpu_dt(DeviceState *dev, CPUState *cs,
> +                                    int *fdt_offset, sPAPRMachineState *spapr)
> +{
> +    PowerPCCPU *cpu = POWERPC_CPU(cs);
> +    DeviceClass *dc = DEVICE_GET_CLASS(cs);
> +    int id = ppc_get_vcpu_dt_id(cpu);
> +    void *fdt;
> +    int offset, fdt_size;
> +    char *nodename;
> +
> +    fdt = create_device_tree(&fdt_size);
> +    nodename = g_strdup_printf("%s@%x", dc->fw_name, id);
> +    offset = fdt_add_subnode(fdt, 0, nodename);
> +
> +    spapr_populate_cpu_dt(cs, fdt, offset, spapr);
> +    g_free(nodename);
> +
> +    *fdt_offset = offset;
> +    return fdt;
> +}
> +
>  static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
>                                        DeviceState *dev, Error **errp)
>  {
> @@ -2307,6 +2370,12 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
>          }
>  
>          spapr_memory_plug(hotplug_dev, dev, node, errp);
> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
> +        if (!smc->dr_cpu_enabled && dev->hotplugged) {
> +            error_setg(errp, "CPU hotplug not supported for this machine");
> +            return;
> +        }
> +        spapr_core_plug(hotplug_dev, dev, errp);
>      }
>  }
>  
> @@ -2366,6 +2435,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
>  
>      smc->dr_lmb_enabled = true;
> +    smc->dr_cpu_enabled = true;
>      fwc->get_dev_path = spapr_get_fw_dev_path;
>      nc->nmi_monitor_handler = spapr_nmi;
>  }
> @@ -2445,6 +2515,7 @@ static void spapr_machine_2_5_class_options(MachineClass *mc)
>  
>      spapr_machine_2_6_class_options(mc);
>      smc->use_ohci_by_default = true;
> +    smc->dr_cpu_enabled = false;
>      SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_5);
>  }
>  
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 9ddf3ce..4c233d7 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -14,6 +14,65 @@
>  #include "qapi/visitor.h"
>  #include <sysemu/cpus.h>
>  
> +void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> +                     Error **errp)
> +{
> +    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine());
> +    sPAPRMachineState *ms = SPAPR_MACHINE(qdev_get_machine());
> +    sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
> +    PowerPCCPU *cpu = &core->threads[0];
> +    CPUState *cs = CPU(cpu);
> +    int id = ppc_get_vcpu_dt_id(cpu);
> +    sPAPRDRConnector *drc =
> +        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, id);
> +    sPAPRDRConnectorClass *drck;
> +    Error *local_err = NULL;
> +    void *fdt = NULL;
> +    int fdt_offset = 0;
> +
> +    if (!smc->dr_cpu_enabled) {
> +        /*
> +         * This is a cold plugged CPU core but the machine doesn't support
> +         * DR. So skip the hotplug path ensuring that the core is brought
> +         * up online with out an associated DR connector.
> +         */
> +        return;
> +    }
> +
> +    g_assert(drc);
> +
> +    /*
> +     * Setup CPU DT entries only for hotplugged CPUs. For boot time or
> +     * coldplugged CPUs DT entries are setup in spapr_finalize_fdt().
> +     */
> +    if (dev->hotplugged) {
> +        fdt = spapr_populate_hotplug_cpu_dt(dev, cs, &fdt_offset, ms);
> +        dev->hotplugged = true;
> +    }
> +
> +    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> +    drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, &local_err);
> +    if (local_err) {
> +        g_free(fdt);
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +
> +    if (dev->hotplugged) {
> +        /*
> +         * Send hotplug notification interrupt to the guest only in case
> +         * of hotplugged CPUs.
> +         */
> +        spapr_hotplug_req_add_by_index(drc);
> +    } else {
> +        /*
> +         * Set the right DRC states for cold plugged CPU.
> +         */
> +        drck->set_allocation_state(drc, SPAPR_DR_ALLOCATION_STATE_USABLE);
> +        drck->set_isolation_state(drc, SPAPR_DR_ISOLATION_STATE_UNISOLATED);
> +    }
> +}
> +
>  static int spapr_cpu_core_realize_child(Object *child, void *opaque)
>  {
>      Error **errp = opaque;
> @@ -30,6 +89,7 @@ static int spapr_cpu_core_realize_child(Object *child, void *opaque)
>      if (*errp) {
>          return 1;
>      }
> +    spapr_cpu_reset(cpu);

This also looks like it belongs in a different patch.

>      return 0;
>  }
> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> index 39f4682..10340e1 100644
> --- a/hw/ppc/spapr_events.c
> +++ b/hw/ppc/spapr_events.c
> @@ -437,6 +437,9 @@ static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t hp_action,
>      case SPAPR_DR_CONNECTOR_TYPE_LMB:
>          hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_MEMORY;
>          break;
> +    case SPAPR_DR_CONNECTOR_TYPE_CPU:
> +        hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_CPU;
> +        break;
>      default:
>          /* we shouldn't be signaling hotplug events for resources
>           * that don't support them
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index b7c5ebd..cc0369e 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -34,6 +34,7 @@
>  
>  #include "hw/ppc/spapr.h"
>  #include "hw/ppc/spapr_vio.h"
> +#include "hw/ppc/ppc.h"
>  #include "qapi-event.h"
>  #include "hw/boards.h"
>  
> @@ -161,6 +162,27 @@ static void rtas_query_cpu_stopped_state(PowerPCCPU *cpu_,
>      rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>  }
>  
> +/*
> + * Set the timebase offset of the CPU to that of first CPU.
> + * This helps hotplugged CPU to have the correct timebase offset.
> + */
> +static void spapr_cpu_update_tb_offset(PowerPCCPU *cpu)
> +{
> +    PowerPCCPU *fcpu = POWERPC_CPU(first_cpu);
> +
> +    cpu->env.tb_env->tb_offset = fcpu->env.tb_env->tb_offset;
> +}
> +
> +static void spapr_cpu_set_endianness(PowerPCCPU *cpu)
> +{
> +    PowerPCCPU *fcpu = POWERPC_CPU(first_cpu);
> +    PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(fcpu);
> +
> +    if (!pcc->interrupts_big_endian(fcpu)) {
> +        cpu->env.spr[SPR_LPCR] |= LPCR_ILE;
> +    }
> +}
> +
>  static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
>                             uint32_t token, uint32_t nargs,
>                             target_ulong args,
> @@ -197,6 +219,8 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
>          env->nip = start;
>          env->gpr[3] = r3;
>          cs->halted = 0;
> +        spapr_cpu_set_endianness(cpu);
> +        spapr_cpu_update_tb_offset(cpu);
>  
>          qemu_cpu_kick(cs);
>  
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 06e6cec..d1a0af8 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -36,6 +36,7 @@ struct sPAPRMachineClass {
>  
>      /*< public >*/
>      bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
> +    bool dr_cpu_enabled;       /* enable dynamic-reconfig/hotplug of CPUs */
>      bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
>  };
>  
> @@ -589,6 +590,9 @@ void spapr_hotplug_req_add_by_count(sPAPRDRConnectorType drc_type,
>  void spapr_hotplug_req_remove_by_count(sPAPRDRConnectorType drc_type,
>                                            uint32_t count);
>  void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp);
> +void spapr_cpu_reset(void *opaque);
> +void *spapr_populate_hotplug_cpu_dt(DeviceState *dev, CPUState *cs,
> +                                    int *fdt_offset, sPAPRMachineState *spapr);
>  
>  /* rtas-configure-connector state */
>  struct sPAPRConfigureConnectorState {
> diff --git a/include/hw/ppc/spapr_cpu_core.h b/include/hw/ppc/spapr_cpu_core.h
> index ddaff6f..9879398 100644
> --- a/include/hw/ppc/spapr_cpu_core.h
> +++ b/include/hw/ppc/spapr_cpu_core.h
> @@ -26,4 +26,6 @@ typedef struct sPAPRCPUCore {
>      PowerPCCPU *threads;
>  } sPAPRCPUCore;
>  
> +void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> +                     Error **errp);
>  #endif
diff mbox

Patch

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 5acb612..6c4ac50 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -603,6 +603,18 @@  static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
     size_t page_sizes_prop_size;
     uint32_t vcpus_per_socket = smp_threads * smp_cores;
     uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine());
+    sPAPRDRConnector *drc;
+    sPAPRDRConnectorClass *drck;
+    int drc_index;
+
+    if (smc->dr_cpu_enabled) {
+        drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, index);
+        g_assert(drc);
+        drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
+        drc_index = drck->get_index(drc);
+        _FDT((fdt_setprop_cell(fdt, offset, "ibm,my-drc-index", drc_index)));
+    }
 
     /* Note: we keep CI large pages off for now because a 64K capable guest
      * provisioned with large pages might otherwise try to map a qemu
@@ -987,6 +999,16 @@  static void spapr_finalize_fdt(sPAPRMachineState *spapr,
         _FDT(spapr_drc_populate_dt(fdt, 0, NULL, SPAPR_DR_CONNECTOR_TYPE_LMB));
     }
 
+    if (smc->dr_cpu_enabled) {
+        int offset = fdt_path_offset(fdt, "/cpus");
+        ret = spapr_drc_populate_dt(fdt, offset, NULL,
+                                    SPAPR_DR_CONNECTOR_TYPE_CPU);
+        if (ret < 0) {
+            error_report("Couldn't set up CPU DR device tree properties");
+            exit(1);
+        }
+    }
+
     _FDT((fdt_pack(fdt)));
 
     if (fdt_totalsize(fdt) > FDT_MAX_SIZE) {
@@ -1181,7 +1203,7 @@  static void ppc_spapr_reset(void)
 
 }
 
-static void spapr_cpu_reset(void *opaque)
+void spapr_cpu_reset(void *opaque)
 {
     sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
     PowerPCCPU *cpu = opaque;
@@ -1622,6 +1644,8 @@  static void spapr_boot_set(void *opaque, const char *boot_device,
 void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
 {
     CPUPPCState *env = &cpu->env;
+    CPUState *cs = CPU(cpu);
+    int i;
 
     /* Set time-base frequency to 512 MHz */
     cpu_ppc_tb_init(env, TIMEBASE_FREQ);
@@ -1646,6 +1670,14 @@  void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
         }
     }
 
+    /* Set NUMA node for the added CPUs  */
+    for (i = 0; i < nb_numa_nodes; i++) {
+        if (test_bit(cs->cpu_index, numa_info[i].node_cpu)) {
+            cs->numa_node = i;
+            break;
+        }
+    }
+
     xics_cpu_setup(spapr->icp, cpu);
     qemu_register_reset(spapr_cpu_reset, cpu);
 }
@@ -1768,6 +1800,7 @@  static void ppc_spapr_init(MachineState *machine)
     char *filename;
     int spapr_cores = smp_cpus / smp_threads;
     int spapr_max_cores = max_cpus / smp_threads;
+    int smt = kvmppc_smt_threads();
 
     if (smp_cpus % smp_threads) {
         error_report("smp_cpus (%u) must be multiple of threads (%u)",
@@ -1834,6 +1867,15 @@  static void ppc_spapr_init(MachineState *machine)
         spapr_validate_node_memory(machine, &error_fatal);
     }
 
+    if (smc->dr_cpu_enabled) {
+        for (i = 0; i < spapr_max_cores; i++) {
+            sPAPRDRConnector *drc =
+                spapr_dr_connector_new(OBJECT(spapr),
+                                       SPAPR_DR_CONNECTOR_TYPE_CPU, i * smt);
+            qemu_register_reset(spapr_drc_reset, drc);
+        }
+    }
+
     /* init CPUs */
     if (machine->cpu_model == NULL) {
         machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
@@ -2267,6 +2309,27 @@  out:
     error_propagate(errp, local_err);
 }
 
+void *spapr_populate_hotplug_cpu_dt(DeviceState *dev, CPUState *cs,
+                                    int *fdt_offset, sPAPRMachineState *spapr)
+{
+    PowerPCCPU *cpu = POWERPC_CPU(cs);
+    DeviceClass *dc = DEVICE_GET_CLASS(cs);
+    int id = ppc_get_vcpu_dt_id(cpu);
+    void *fdt;
+    int offset, fdt_size;
+    char *nodename;
+
+    fdt = create_device_tree(&fdt_size);
+    nodename = g_strdup_printf("%s@%x", dc->fw_name, id);
+    offset = fdt_add_subnode(fdt, 0, nodename);
+
+    spapr_populate_cpu_dt(cs, fdt, offset, spapr);
+    g_free(nodename);
+
+    *fdt_offset = offset;
+    return fdt;
+}
+
 static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
                                       DeviceState *dev, Error **errp)
 {
@@ -2307,6 +2370,12 @@  static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
         }
 
         spapr_memory_plug(hotplug_dev, dev, node, errp);
+    } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
+        if (!smc->dr_cpu_enabled && dev->hotplugged) {
+            error_setg(errp, "CPU hotplug not supported for this machine");
+            return;
+        }
+        spapr_core_plug(hotplug_dev, dev, errp);
     }
 }
 
@@ -2366,6 +2435,7 @@  static void spapr_machine_class_init(ObjectClass *oc, void *data)
     mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
 
     smc->dr_lmb_enabled = true;
+    smc->dr_cpu_enabled = true;
     fwc->get_dev_path = spapr_get_fw_dev_path;
     nc->nmi_monitor_handler = spapr_nmi;
 }
@@ -2445,6 +2515,7 @@  static void spapr_machine_2_5_class_options(MachineClass *mc)
 
     spapr_machine_2_6_class_options(mc);
     smc->use_ohci_by_default = true;
+    smc->dr_cpu_enabled = false;
     SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_5);
 }
 
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index 9ddf3ce..4c233d7 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -14,6 +14,65 @@ 
 #include "qapi/visitor.h"
 #include <sysemu/cpus.h>
 
+void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
+                     Error **errp)
+{
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine());
+    sPAPRMachineState *ms = SPAPR_MACHINE(qdev_get_machine());
+    sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
+    PowerPCCPU *cpu = &core->threads[0];
+    CPUState *cs = CPU(cpu);
+    int id = ppc_get_vcpu_dt_id(cpu);
+    sPAPRDRConnector *drc =
+        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, id);
+    sPAPRDRConnectorClass *drck;
+    Error *local_err = NULL;
+    void *fdt = NULL;
+    int fdt_offset = 0;
+
+    if (!smc->dr_cpu_enabled) {
+        /*
+         * This is a cold plugged CPU core but the machine doesn't support
+         * DR. So skip the hotplug path ensuring that the core is brought
+         * up online with out an associated DR connector.
+         */
+        return;
+    }
+
+    g_assert(drc);
+
+    /*
+     * Setup CPU DT entries only for hotplugged CPUs. For boot time or
+     * coldplugged CPUs DT entries are setup in spapr_finalize_fdt().
+     */
+    if (dev->hotplugged) {
+        fdt = spapr_populate_hotplug_cpu_dt(dev, cs, &fdt_offset, ms);
+        dev->hotplugged = true;
+    }
+
+    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
+    drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, &local_err);
+    if (local_err) {
+        g_free(fdt);
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    if (dev->hotplugged) {
+        /*
+         * Send hotplug notification interrupt to the guest only in case
+         * of hotplugged CPUs.
+         */
+        spapr_hotplug_req_add_by_index(drc);
+    } else {
+        /*
+         * Set the right DRC states for cold plugged CPU.
+         */
+        drck->set_allocation_state(drc, SPAPR_DR_ALLOCATION_STATE_USABLE);
+        drck->set_isolation_state(drc, SPAPR_DR_ISOLATION_STATE_UNISOLATED);
+    }
+}
+
 static int spapr_cpu_core_realize_child(Object *child, void *opaque)
 {
     Error **errp = opaque;
@@ -30,6 +89,7 @@  static int spapr_cpu_core_realize_child(Object *child, void *opaque)
     if (*errp) {
         return 1;
     }
+    spapr_cpu_reset(cpu);
 
     return 0;
 }
diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
index 39f4682..10340e1 100644
--- a/hw/ppc/spapr_events.c
+++ b/hw/ppc/spapr_events.c
@@ -437,6 +437,9 @@  static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t hp_action,
     case SPAPR_DR_CONNECTOR_TYPE_LMB:
         hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_MEMORY;
         break;
+    case SPAPR_DR_CONNECTOR_TYPE_CPU:
+        hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_CPU;
+        break;
     default:
         /* we shouldn't be signaling hotplug events for resources
          * that don't support them
diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index b7c5ebd..cc0369e 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -34,6 +34,7 @@ 
 
 #include "hw/ppc/spapr.h"
 #include "hw/ppc/spapr_vio.h"
+#include "hw/ppc/ppc.h"
 #include "qapi-event.h"
 #include "hw/boards.h"
 
@@ -161,6 +162,27 @@  static void rtas_query_cpu_stopped_state(PowerPCCPU *cpu_,
     rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
 }
 
+/*
+ * Set the timebase offset of the CPU to that of first CPU.
+ * This helps hotplugged CPU to have the correct timebase offset.
+ */
+static void spapr_cpu_update_tb_offset(PowerPCCPU *cpu)
+{
+    PowerPCCPU *fcpu = POWERPC_CPU(first_cpu);
+
+    cpu->env.tb_env->tb_offset = fcpu->env.tb_env->tb_offset;
+}
+
+static void spapr_cpu_set_endianness(PowerPCCPU *cpu)
+{
+    PowerPCCPU *fcpu = POWERPC_CPU(first_cpu);
+    PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(fcpu);
+
+    if (!pcc->interrupts_big_endian(fcpu)) {
+        cpu->env.spr[SPR_LPCR] |= LPCR_ILE;
+    }
+}
+
 static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
                            uint32_t token, uint32_t nargs,
                            target_ulong args,
@@ -197,6 +219,8 @@  static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
         env->nip = start;
         env->gpr[3] = r3;
         cs->halted = 0;
+        spapr_cpu_set_endianness(cpu);
+        spapr_cpu_update_tb_offset(cpu);
 
         qemu_cpu_kick(cs);
 
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 06e6cec..d1a0af8 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -36,6 +36,7 @@  struct sPAPRMachineClass {
 
     /*< public >*/
     bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
+    bool dr_cpu_enabled;       /* enable dynamic-reconfig/hotplug of CPUs */
     bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
 };
 
@@ -589,6 +590,9 @@  void spapr_hotplug_req_add_by_count(sPAPRDRConnectorType drc_type,
 void spapr_hotplug_req_remove_by_count(sPAPRDRConnectorType drc_type,
                                           uint32_t count);
 void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp);
+void spapr_cpu_reset(void *opaque);
+void *spapr_populate_hotplug_cpu_dt(DeviceState *dev, CPUState *cs,
+                                    int *fdt_offset, sPAPRMachineState *spapr);
 
 /* rtas-configure-connector state */
 struct sPAPRConfigureConnectorState {
diff --git a/include/hw/ppc/spapr_cpu_core.h b/include/hw/ppc/spapr_cpu_core.h
index ddaff6f..9879398 100644
--- a/include/hw/ppc/spapr_cpu_core.h
+++ b/include/hw/ppc/spapr_cpu_core.h
@@ -26,4 +26,6 @@  typedef struct sPAPRCPUCore {
     PowerPCCPU *threads;
 } sPAPRCPUCore;
 
+void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
+                     Error **errp);
 #endif